Platform question

How do you make a platform move down when you stand on it and move up to it's original position when you don't stand on it?

You could check if the player is on top of it using overlapping at offset and attach the appropriate actions to that..

How do you make a platform move down when you stand on it and move up to it's original position when you don't stand on it?

Something like this?

https://dl.dropboxusercontent.com/u/3430669/bouncyplatform.capx